Compiler Error C2899

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The latest version of this topic can be found at Visual Studio 2017 Documentation. typename cannot be used outside a template declaration

The typename keyword can be used only in a template definition or declaration. In a template declaration, it can be used in two ways:

// C2899.cpp  
// compile with: /c  
template<typename T>   
class X {};  
  
// Another way  
template<class T>   
struct XX {  
   typename T::A a;   // T::A is a type  
};

The following sample generates C2899:

// C2899b.cpp  
// compile with: /c  
struct Y {  
   typedef int B;  
   typename Y::B b;   // C2899  
};